Three-dimensional Finite Element Analysis In Occipital Condylar Fracture

Objective:Establishing three-dimensional finite element model of normal upper cervical vertebra(include occipital condyle),using finite element analysis software to study the injury mechanism of occipital condylar fracture,and verifing classification of occipital condylar fracture,to provide theory evidence and guidance for the treatment of occipital condylar fracture,and provide a mechanical model for the biomechanical study of cervical vertebra and craniocervical junction.Methods:A healthy adult male volunteer who examined and completed the neck CT scan at the outpatient clinic of our hospital was selected as the study object,and no history of neck trauma,surgery,deformity,rheumatism immunity,tumor,tuberculosis and other medical history.The CT images were imported into the software to establish a three-dimensional finite element model of the upper cervical vertebra.The normal physiological activities of cervical vertebra were simulated in the finite element software,and the motion degrees of each segment ofupper cervical vertebra were calculated under different conditions of flexion and extension,lateral bending and rotation,and the experimental results were compared with vitro biomechanical experimental data.After the model was validated,axial compression and lateral bending rotational violence were loaded on the model to simulate the force of trauma,and the stress changes of the fracture location and surrounding stress were determined by analyzing the stress cloud map.Three kinds of occipital condylar fracture models were established on the basis of the normal upper cervical vertebra model,and the same boundary conditions and loading methods were applied to the fracture model.The finite element analysis was carried out to study the stress distribution,and the stability of the fracture model was evaluated by calculating the mobility of each segment of the upper cervical vertebra.Result:1.A three-dimensional model of the C0-C3 segment of the upper cervical spine was successfully established in this experiment.The model consists of 366820 tetrahedral units and 83521 nodes.After verification,the data of motion of each segment of cervical spine in different motion states were consistent with the vitro experimental data,and the results of stress distribution were consistent with Brolin's experimental results.This model can be used for subsequent finite element analysis.2.During the movement of the normal upper cervical spinemodel,the stress was concentrated around the anterior and posterior edges of the ipsilateral vertebral body,the ipsilateral lateral mass,the anterior and posterior arches of the atlas and the axial odontoid process,and there was a tendency to spread to the contralateral and surrounding structures.3.Under flexion and extension and lateral flexion,the stress of the skull base was mainly distributed in the vicinity of the ipsilateral occipital condyle.The stress was concentrated in the nearby of the contralateral occipital condyle under rotation.4.When the skull is subjected to axial violence,the stress in the vicinity of the bilateral occipital condyle increased sharply compared with that in the absence of external force,and concentrated nearby of occipital condyle.The stress is all around of right occipital condyle increased significantly when the right occipital condyle was bent and rotated violently,and the stress was mainly concentrated around the occipital condyle.5.In the fracture model,the stress on the left occipital condyle was lost to different degrees,while the stress on the right occipital condyle increased in different amplitude,and the change was the largest in the type III occipital condylar fracture model.6.In the fracture model,the range of motion of each segment of cervical vertebra increased to different degrees,with the greatest change in C0-C1 segment.Conclusion:1.When axial compression violence occurs,the stress is concentrated on the edge of the occipital condyle,and the possibility of local comminuted or massive fracture of the occipital condyle is great.At this time,the ligament is intact and the fracture tends to be stable,which accords with the mechanism of I and II occipital condylar fractures.2.In the case of lateral bending and rotational violence,the stress is concentrated around the occipital condyle,and the ligament is damaged,the possibility of avulsion fracture is great.The fracture is unstable,which accords with the mechanism of type III occipital condylar fracture.3.The increase of joint motion after fracture may be related to structural loss and stress bias.